Oh man, SUPER insane for sure. In my opinion, inverted box is somewhere between 4.25-4.5 ball difficulty. Inverted sprung cascade is somewhere a little ~6.25 ball difficulty. Inverted sprung fountain (https://www.instagram.com/p/BiFhmhsDHVU/) is probably about 7b difficulty. I can't run fully inverted sprung cascade for long enough to give it a nice number like the others, but it's the only one among that group that I have to mentally really psych myself up for and can't follow in real-time. It's much harder than inverted sprung fountain.

Who knows, though. Maybe I went through the learning process of it poorly and other ways would knock down its difficulty considerably. And there's always the added difficulty of being the first to do it. It'll be easier to gauge its difficulty when a few more people can wrap their hands around it.

There is a pattern that I thought of at IJA 2013 that seemed so conceptually clear (but non-obvious) and disastrously difficult. ~4 years ago I realized that there would be three interesting stepping stone patterns along the way. They were all so far above my skill level at the time, and I'm still not convinced they're all doable by me, but I set the very long-term goal to run them all before retiring from juggling. I reckon I can probably make progress on them until my early-mid thirties (other parts of life permitting), so there's slight urgency.

Fully inverted sprung cascade (FISC) is the first of those four patterns! In my opinion, patterns 2 and 3 aren't as cool as FISC, but pattern 4 would be a dream. I don't want to expose the later three patterns just yet, sorry!

Amazing stuff Mike. It almost looks 'easy' in some kind of strange way. I can see there is almost no time to get from one throw to the next though, so it looks almost impossible too. You are truly pushing the boundaries!